Propulsion Systems
Major US Airline Year 2000 Operating Costs
Cost per ASM = 9.75 ¢
Aircraft Fuel
13%
Engine Maint. Material
& OSR
2%
Engine Ownership
3%
Salaries
40%
Airframe Ownership
10%
Airframe Maint. Material
&OSR
2%
Landing fees and other
rents
5%
Other
13%
"Other" includes contracted services,
asset write-downs, other non-recurring items
Passenger service
3%
Selling expenses
9%
Three Class Seating
3000 nm Trip
Airplane Operating Cost Comparison
30%
20%
g
in
as
s
at
e
S
15%
nt
a
st
n
o
=C
e
cr
In
10%
s
at
Se
Relative Cash DOC per Seat
25%
Current State-of-Art
5%
0%
-5%
0%
1
-
-10%
-15%
-20%
-15%
GOAL
-10%
-5%
0%
5%
10%
15%
20%
25%
Relative Cash DOC per Trip
30%
35%
40%
45%
Typical Engine-Related Airline Cost Breakdown
Initial Cost (List)
33%
Fuel Cost
54%
Maintenance Cost
13%
777-200ER/PW4090
$0.75/gal Fuel Price
Thrust Sizing Requirements
Y Limit
TOGW
T/W
W/S
X Limit
• Number of Engines
• Aircraft Max Take Off Gross Weight
• Take Off Field Length
• Time to Climb
• Cruise Altitude and Mach Number
• Lift to Drag of Wing
• Aircraft Potential Growth
Basic engine relationships
Thrust = (Velocity of exhaust - velocity of aircraft)
Mass
Overall engine efficiency = K thermal X K propulsive
Overall Engine Efficiency Includes Two Processes:
Energy Conversion and Thrust Production
Gas Generator
Available
Propulsion
Energy
Fuel Input
K overall
=
Kthermal
X
Kpropulsive Thermal efficiency measures the process of converting chemical
energy of the fuel into energy available for propulsion
- Function of overall pressure ratio and component efficiencies h
s
Current engines at 40:1
overall pressure ratio
Future engines at 60:1
overall pressure ratio
Propulsive efficiency measures the process of converting energy
available for propulsion into useful propulsive power
Gas Generator
Gas Generator
Turbofan
or
Turboprop
Gas Generator
Kpropulsive
100% as
Vexhaust
Vo
Lower specific thrust is fundamental to improving fuel
economy
Engine efficiency
goodness
Fuel
economy
Drag/thrust
Weight/thrust
Specific thrust (lb /lb mass)
Increasing bypass ratio
Commercial Turbofan